In December 2008, RCM&E magazine published a build article and plans for Dave Royds' (MrFlash) big 55" Edge 540T foamie. After sitting on the plans for almost a year and a half, I finally gathered all the gear and started building it. The big difference is that I had a bunch of FFF and depron left over from previous builds, so that's what I used instead of EPP. I can't publish the actual plans, but you should still be able to get back issues of the magazine through http://www.myhobbystore.co.uk/produc...-december-2008.

First, some statistics:

Wingspan: 55.5" (the extra .5" was depron that I added to the tips, intending to sand it round, but leaving it flat for now)

Final weight: 1170g (~2.57 lbs) (It will probably add another ounce or so after I finish painting the wings.)

Tubes of UHU Creativ/Por glue used: 4

1/2 oz containers of foam-safe CA used: 1

2 full sheets of FFF, plus random scrap pieces from previous builds

2 sheets of 2mm depron

I took the plans from the magazine to Fedex Office to have the front and back duplicated separately so I could cut out the templates without messing up the original. Since I was building with 6mm FFF instead of 9mm EPP, I had to keep in mind that some of the internal formers will need to be slightly increased in size in order to maintain the outer dimensions from the plans. So I usually cut them oversize then trim to fit. I also sheeted the wing with 2mm depron instead of EPP, and put a 3mm carbon tube along the leading edge of the wing, which is a technique I learned from my GloStik build. Because FFF and depron is stiffer than EPP, I was able to eliminate some of the carbon reinforcement in the plans, which probably saved me a few grams of weight.

The only other major issue I had was the carbon wing tubes. I ordered 12mm and 10mm tubes from HobbyKing along with the electronics. The 12mm tube has a 10mm inner diameter, but the 10mm tube was just a little too big to slide through easily, so I had to sand it down just a bit.

Some points of interest in this build:

Tail group and control surfaces are laminated from two pieces of FFF, or in the case of the ailerons, FFF with depron on both sides, which makes the piece much stiffer than a single piece of foam alone. It probably wasn't necessary, but I did embed carbon flats in the h-stab, v-stab, rudder, and elevator just for good measure.

All control surfaces surfaces are tapered/airfoiled. I started with the ailerons, and made the mistake of trying to sand the taper into the FFF with a power sander. Besides creating a lot of dust, this would have been fine if I hadn't already put the depron sheeting on the opposite side. However the end result was that the depron got some ugly scratches on it since it was vibrating on my cutting table. I was able to fill most of those with lightweight spackle, but what worked better for me in the end, with the rudder and elevator, was to simply use a sanding block. I would sand each side down to an appropriate angle, then glue the two pieces together.

I like easy access to the motor, so the nose piece is removable. It's secured with tiny 3mm rare earth magnets and has a couple of carbon alignment rods to keep it from moving around. This came in handy when I had to remove the motor to drill the battery cooling holes.

A steerable tail wheel made a lot of sense for this plane, so that it could have good ground handling. I experimented with several designs, none of which were heavy duty enough, until I finally settled on something simple with a couple of pieces of ply to reinforce it. There is a photo of the one I finally wound up with.

Wing servos are embedded in the wings. I did this for no particular reason, I just thought it might be a little cleaner. Also, the servo cutouts really support the servo well and keep it from moving, so there is very little glue needed to keep it in place. I figured that if I need to replace the servos, it's easy enough to make a little removable access hatch; I actually had to do this to one wing when the servo extension got disconnected.

Battery cooling is an issue. On my second and third flights, it was about 100 degrees F outside, and the batteries came down really hot. I realized that I just didn't have any cooling in the battery bay, so I had to drill battery cooling holes in the firewall, as well as constructing air output channels along the sides of the cockpit. This directed the hot air to the back of the fuselage let it escape out of the opening over the h-stab. If I thought ahead, I could have left the space under the cockpit floor completely open, which would have saved me a bit of work.

Based on my previous experience with the Big Nasty build, I made a plywood landing gear box. The landing gear slides in and is secured with another piece of plywood and a screw that goes through the landing gear box. Since I no longer had the Big Nasty, but still had the music wire landing gear left over, I decided to duplicate this setup on the Edge. This works great, but it seems that there is a bigger difference between a 22oz plane and a 42oz plane than I thought; it appears that the music wire I used just isn't thick enough to handle the stress of landing a 42oz plane on grass without bending, so I will be looking for a beefier undercarriage.

MrFlash used an internal servo tray and ran long pushrods to the elevator and rudder. I'm not a fan of using long pushrods, especially for a 3D plane, so I put the rudder and elevator servos under the h-stab and ran servo extensions to the receiver. I did this knowing that having the servos so far aft might make it difficult to have the CG in the right place. During the build, I also added a second layer of FFF behind the servo mounting locations to reinforce the foam and keep the servo from wiggling during operation.

I used a ball link from my 450 heli on the rudder servo, because the servo movement is 90 degrees to the rudder movement. This ensures that the pushrod is never forced to flex because of the rudder movement, and avoids placing additional stress on the rudder servo.

Here is the final equipment list:

Turnigy TR35-42D 1000 kv motor, JXF 12x6 prop

Welgard 40A ESC with 3A BEC

4x HXT900 servos, 4 servo extensions

U-Can-Do 3D .46 canopy, trimmed to fit.

20 3mm x 1mm rare earth magnets to secure the nose piece and hatches

Spektrum AR6100 receiver

BTW, yes, I am using cheap HXT900 servos instead of Hitec HS-65 MG servos that MrFlash used in his build. This is a personal choice because I am familiar with these servos, have used them in a number of builds, and feel that they can do the job. In the three flights I've had with the plane so far, they have certainly been up to the task.

Painting:

I had never painted an entire plane before, opting for either unpainted or a Sharpie paint job. For the Edge, I decided that I just couldn't have this be a blue plane with white wings, so I bought myself an early birthday present: a cheap Harbor Freight air brush and compressor. After learning the basic techniques on a spare sheet of FFF, I was ready to lay down some color. The big mistake I made was to not paint the entire fuselage white before putting the orange on the top half, because the blue color from the FFF mixed with the orange and made it darker than it should have been. This created problem because the wings were covered in white depron, and putting the orange onto white depron would have been very noticeably lighter. After trying several shades of orange from the store, I finally mixed in a couple drops of black to darken the original orange color before painting the wings.

For the checkerboard on the bottom of the wings, I cut acetate (transparency sheets), coated it one side with 3M 77 spray, let it dry, then stuck it on the depron before painting. This works very well and the acetate is easily removable afterward. I did the same for the lettering on the top. Then I traced the outlines with Sharpie before spraying a coat of Minwax Polycrylic.

Maiden report:

I maidened the Edge on July 18th, 2010. Conditions were not ideal for a maiden: close to 100 degrees F, with probably 10-15 mph winds. However I was just dying to see how it flies and couldn't wait any longer.

My CG was slightly aft of the 3D CG point on the plans, so it flew tail heavy. You can kind of see this in the video. It was also a short maiden, because during one of the rolls it seems I lost an aileron. When it came down I noticed that one of my home-made 1/32 ply control horns broke. Oops! I promptly replaced the control horns with plastic control horns cut from a plastic gift card.

Second and third flights were done on another 100-degree day about a week after the maiden, but this time the winds were below 10mph. I adjusted the CG forward by putting 3oz of ballast in the ESC compartment, right behind the firewall. This allowed my CG to end up just slightly behind the wing tube. Unfortunately I couldn't get video of those flights, but the plane flew significantly better. Total weight increased to almost 42 oz, but the power system handles it no problem. As I mentioned above, this is when I realized the battery cooling issue and made some big air holes in the firewall, for both the battery and ESC compartments. I think after a couple more flights to adjust the aileron differential, and some beefier landing gear, I will be very happy with this plane.

Fourth flight report:

I've been shopping around for landing gear online, and finally went to the LHS to see if they had anything. I picked up some 1/8" music wire, which is definitely thicker and stronger than the 3/32" wire I was using. The 1/32" difference doesn't sound like a lot, but it's 33% thicker than the old wire. I had never worked with music wire this thick before, and it was so strong that I had to use a mini-torch to heat it so I could bend it into shape. The best part is that it still slides right into my landing gear box, so no modification was necessary on the plane.

The more difficult task was mounting the wheel pants, which I fashioned out of foam as well. I decided to make them easily removable, so I could fly off grass that would normally tear them off, which meant attaching a mounting plate to the inside wheel collar. I made the mounting plate out of aluminum flashing, which you can't solder with regular electronics solder, so I finally resorted to Gorilla Glue brand CA, which seems to be holding pretty well so far.

After a quick flight with this setup, the new landing gear seems to be holding up much better, and the battery cooling holes are doing their job, but I noticed that the ESC cooling is still inadequate. Before the next flight, I will have to figure out how to provide better cooling to the ESC. Also since I figured out how to put the spinner on, motor cooling is now an issue as well because the spinner blocks all direct air flow to the motor. The spinner will probably have to come off for the next flight. Either that, or I have to stop flying when it's 100 degrees outside.

Yep it looked a little twitchy, but you did a good job of keeping it level in that wind. Just play around with the cg like you are doing then you'll find the sweet spot.

I think my cg was bang on the wing tube for "normal" stuff and about 3/4" back for 3D. Trim it for level flight when its not windy then flip it inverted. When it flys without climbing right way up and inverted thats a pretty good starting point.